排序方式: 共有21条查询结果,搜索用时 15 毫秒
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Hilton ST Motherwell WB Potier P Pradet C Selwood DL 《Bioorganic & medicinal chemistry letters》2005,15(9):2239-2242
A range of thiyl radicals derived from the reduced form of epidithiodiketopiperazines (ETPs) act as polarity reversal catalysts for the hydrosilylation of an enol lactone but not for H-atom abstraction from a model ribose ester. 相似文献
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Molecular interactions in 32 crystal structures of pyrimidine nucleosides and nucleoside derivatives have been studied in terms of empirical van der Waals' energy. The stacking patterns have been classified into three types according to the symmetry operations involved within the pattern. Halogen and sulphur atoms were included in the calculations where necessary. Model columns of stacked molecules were set up in a computer calculation giving the energy for different amounts of base overlap. There was a tendency for the crystal positions of the molecules to agree with the minima of the energy maps, which showed the predominance of the van der Waals' forces in determining the base-stacking arrangement. The position of the energy minimum was correlated with the molecular conformation defined by the C-N glycosidic torsion angle. 相似文献
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Blaney Davidson EN Scharstuhl A Vitters EL van der Kraan PM van den Berg WB 《Arthritis research & therapy》2005,7(6):R1338-R1347
Osteoarthritis (OA) is a common joint disease, mainly effecting the elderly population. The cause of OA seems to be an imbalance
in catabolic and anabolic factors that develops with age. IL-1 is a catabolic factor known to induce cartilage damage, and
transforming growth factor (TGF)-beta is an anabolic factor that can counteract many IL-1-induced effects. In old mice, we
observed reduced responsiveness to TGF-beta-induced IL-1 counteraction. We investigated whether expression of TGF-beta and
its signaling molecules altered with age. To mimic the TGF-beta deprived conditions in aged mice, we assessed the functional
consequence of TGF-beta blocking. We isolated knee joints of mice aged 5 months or 2 years, half of which were exposed to
IL-1 by intra-articular injection 24 h prior to knee joint isolation. Immunohistochemistry was performed, staining for TGF-beta1,
-2 or -3, TGF-betaRI or -RII, Smad2, -3, -4, -6 and -7 and Smad-2P. The percentage of cells staining positive was determined
in tibial cartilage. To mimic the lack of TGF-beta signaling in old mice, young mice were injected with IL-1 and after 2 days
Ad-LAP (TGF-beta inhibitor) or a control virus were injected. Proteoglycan (PG) synthesis (35S-sulfate incorporation) and PG content of the cartilage were determined. Our experiments revealed that TGF-beta2 and -3 expression
decreased with age, as did the TGF-beta receptors. Although the number of cells positive for the Smad proteins was not altered,
the number of cells expressing Smad2P strongly dropped in old mice. IL-1 did not alter the expression patterns. We mimicked
the lack of TGF-beta signaling in old mice by TGF-beta inhibition with LAP. This resulted in a reduced level of PG synthesis
and aggravation of PG depletion. The limited response of old mice to TGF-beta induced-IL-1 counteraction is not due to a diminished
level of intracellular signaling molecules or an upregulation of intracellular inhibitors, but is likely due to an intrinsic
absence of sufficient TGF-beta receptor expression. Blocking TGF-beta distorted the natural repair response after IL-1 injection.
In conclusion, TGF-beta appears to play an important role in repair of cartilage and a lack of TGF-beta responsiveness in
old mice might be at the root of OA development. 相似文献
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R Simões WB Feitosa CM Mendes AC Nicacio FRO de Barros 《Biotechnic & histochemistry》2013,88(3):79-83
Sperm chromatin integrity is essential for accurate transmission of male genetic information, and normal sperm chromatin structure is important for fertilization. Protamine is a nuclear protein that plays a key role in sperm DNA integrity, because it is responsible for sperm DNA stability and packing until the paternal genome is delivered into the oocyte during fertilization. Our aim was to investigate protamine deficiency in sperm cells of Bos indicus bulls (Nelore) using chromomycin A3 (CMA3) staining. Frozen semen from 14 bulls were thawed, then fixed in Carnoy's solution. Smears were prepared and analyzed by microscopy. As a positive control of CMA3 staining, sperm from one bull was subjected to deprotamination of nuclei. The percentage of CMA3-positive bovine sperm did not vary among batches. Only two bulls showed a higher percentage of CMA3-positive sperm cells compared to the others. CMA3 is a simple and useful tool for detecting sperm protamine deficiency in bulls. 相似文献
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The exact pathogenesis of Parkinson's disease (PD) is still unknown and proper mechanisms that correspond to the disease remain unidentified. It is understood that PD is age-related; as age increases, the chance of onset responds accordingly. Although there are no current means of curing PD, the understanding of reactive oxygen species (ROS) provides significant insight to possible treatments. Complex I deficiencies of the respiratory chain account for the majority of unfavorable neural apoptosis generation in PD. Dopaminergic neurons are severely damaged as a result of the deficiency. Symptoms such as inhibited cognitive ability and loss of smooth motor function are the results of such impairment. The genetic mutations of Parkinson's related proteins such as PINK1 and LRRK2 contribute to mitochondrial dysfunction which precedes ROS formation. Various pathways are inhibited by these mutations, and inevitably causing neural cell damage. Antioxidants are known to negate the damaging effects of free radical overexpression. This paper expands on the specific impact of mitochondrial genetic change and production of free radicals as well as its correlation to the neurodegeneration in Parkinson's disease. 相似文献
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The genome of Rhizobium leguminosarum has recognizable core and accessory components 总被引:3,自引:0,他引:3
Young JP Crossman LC Johnston AW Thomson NR Ghazoui ZF Hull KH Wexler M Curson AR Todd JD Poole PS Mauchline TH East AK Quail MA Churcher C Arrowsmith C Cherevach I Chillingworth T Clarke K Cronin A Davis P Fraser A Hance Z Hauser H Jagels K Moule S Mungall K Norbertczak H Rabbinowitsch E Sanders M Simmonds M Whitehead S Parkhill J 《Genome biology》2006,7(4):R34-20